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Acknowledgements : AZRise; The National Science Foundation STC MDITR Grant#0120967 Automated photovoltaic cell characterization system A.Guilmo, J. Roberts, K. Yamnitzkiy, P. A. Blanche, R. A. Norwood, N. Peyghambarian, M. Fallahi College of Optical Sciences, University of Arizona The accurate measurement of the characteristics of a wide range of solar cells based on different technologies, from silicon to polymers, requires a standardized testing process. The existing photovoltaic devices use thin films, multi-junctions, quantum wells or dots and various semiconductor or organic materials depending on the cost, efficiency, and flexibility desired. The measurements on reference cells that have been made agree with NREL calibration measurements to better than 0.9% for the fill factors and better than 3.1% for the efficiencies, showing the excellent accuracy of our system. This poster describes in detail the important solar cell parameters to take into account and the key elements of our characterization system. The fill-factor FF describes how close the maximum power produced by the photodiode is to the ideal diode power. (FF < 1) It is then used to calculate the efficiency: I SC : short-circuit current + – V OC : open-circuit voltage Solar Cell Characteristics Just outside of the atmosphere, solar radiation has an irradiance of 1358 W/m 2 . Typically 600 – 1000 W/m 2 when incident on earth’s surface. earth’s surface The Solar Spectrum Standard Spectra: For reliable testing, standards have been set for the spectra to be used for Photovoltaics. • AM 1.5 chosen because it most closely matches the average spectrum across the United States. • 1 Sun standard is 1000 W/m 2 The Solar Simulator Silicon Cell Response curve The system The Testing Process voltage amount to be source to the cell SourceMeter LabView Program sources voltage cell current data SourceMeter current produced in the circuit temperature control Adjust to be more than I SC Test cell information Adjusted to be near but above the V OC The User Interface Organic Solar Cell Testing Capability The test bed is located inside an enclosure with controlled atmosphere. Temperature, humidity and the air composition (e.g. no oxygen) can be controlled. Peltier device to control the temperature Some Results Reference Cell 0.9% difference in fill factor, 2.5% difference in the ratio of the efficiencies Excellent agreement with NREL measurements was achieved The Solar Simulator provides a uniform collimated beam of light with a spectrum close to the AM 1.5 standard. The LabView program generates a cell information report with the I-V curves. Absorption: The difference between the solar spectrum and the absorption spectrum of the cell introduces losses and generates heat.
